1) Field of the Invention
The present invention relates to an optical device which is used for optical communication and optical information processing, and which outputs, controls, detects, or introduces a multi-wavelength laser light or a tunable laser light using two-dimensional slab photonic crystal, to an optical device manufacturing method, and to a semiconductor laser oscillator.
2) Description of the Related Art
A laser module used in conventional multi-wavelength lasers, tunable lasers or wavelength-selectable lasers includes laser diodes that output laser lights of different wavelengths, a multi-mode interference (MMI) optical coupler that multiplexes the laser lights output from the laser diodes, and a semiconductor optical amplifier (SOA) that amplifies the laser light multiplexed. The laser diodes are arranged in parallel and constituent elements of the laser diodes are connected to one another by a waveguide. In the conventional laser module, the laser lights output from all of the laser diodes or some of the laser diodes are multiplexed by the MMI optical coupler, amplified to a predetermined signal level by the SOA, and then output (see, for example, “Wavelength-Selectable LD module with Multi-Wavelength Monitor of 50 GHz Spacing”, Tadanori IWAFUJI et al, Proceedings of the Electronics Society Conference, the Institute of Electronics, Information, and Communication Engineers, 2001, p. 165).
However, because the respective laser diodes are arranged in parallel, it is necessary to form electrodes necessary to drive or control the laser diodes in an overlapped fashion. As a result, the structure of the laser module becomes complicated and the manufacturing process becomes cumbersome.
In the technology disclosed in the above-mentioned literature, the laser lights from the laser diodes are output from a single emission port and multiplexed with an MMI optical coupler. However, in that case, the more the number of wavelengths is, the greater the connection loss of the MMI optical coupler becomes. As a result, addition of a SOA becomes necessary so that the efficiency of the laser module lowers. Also, an active layer is provided in each laser diode so that, if the laser module is employed as the tunable laser, the laser diodes can merely pump their active layers independently. In addition, since the SOA is integrally provided with the laser diodes, a device size of the laser module is disadvantageously made large. Further, the conventional optical devices that use the slab photonic crystal are inferior in radiation characteristics. It is difficult for an active device such as a laser, in particular, to realize high power output because of its limit to self radiation.